1. Field of the Invention
The present invention relates to a method and apparatus for extruding unvulcanized rubber, in which an unvulcanized rubber member comprised of at least two kinds of unvulcanized rubbers is extruded.
2. Description of the Related Art
In an automobile pneumatic tire, there are some cases in which a rubber chafer comprised of hard rubber may be provided at the outer side of a tire bead portion so as to increase rigidity of the bead portion.
An upper end of the rubber chafer is connected to a side-wall rubber layer which forms a side wall of the tire.
However, there are cases in which, because the bead portion is repeatedly subjected to bending deformation when the vehicle is running, the rubber chafer and the side-wall rubber layer are separated from each other.
In order to solve the aforementioned problem, it has been considered that an area in which the rubber chafer and the side-wall rubber layer are connected can be increased, and a pneumatic tire having a cross sectional configuration as shown in FIG. 7 has been proposed.
In the pneumatic tire having the cross sectional configuration shown in FIG. 7, an inner portion 106A provided at a radial-direction inner side of a side-wall rubber layer 106 which forms a side wall 104, and an outer portion 106B provided at an outer side of the side-wall rubber layer 106 are formed so as to cover inner and outer surfaces, in an axial direction of the tire, of a rubber chafer 102 tapered in an upward direction, and an area in which the side-wall rubber layer 106 and the rubber chafer 102 are connected is increased so as to strengthen the junction between the side-wall rubber layer 106 and the rubber chafer 102.
In order to manufacture such a pneumatic tire, in a process for producing a green tire, a rubber extruded member 108 in which the unvulcanized side-wall rubber layer 106 and the unvulcanized rubber chafer 102 having the cross sectional configuration as shown in FIG. 8 are integrated with each other is produced. Thereafter, a rubber sheet 110 comprised of unvulcanized rubber of the same kind as the side-wall rubber layer 106 is adhered so as to cover a region of the rubber extruded member 108 in the vicinity of the end of the rubber chafer 102.
The rubber extruded member 108 with the rubber sheet 110 adhered thereto is applied to an outer surface of a carcass of a tire case in a production process. Thus, the pneumatic tire is manufactured.
However, there conventionally existed a problem that equipment for adhering the rubber sheet 110 or a process for adhering the sheet may be required, and equipment investment and stock handling of the rubber sheet 10 may also increase.
Further, because the thick rubber sheet 110 is adhered to the rubber extruded member 108, a stepped portion 112 is formed on the surface of the rubber extruded member 108, as shown in FIG. 8. For this reason, air in the stepped portion 112 may cause bare. Moreover, losses due to spoiled products caused by incorrect setting may also increase.